5.1 Overview of Convection Heat tran using moveme fluids is called convection. In natural convection, the flow is induced by the differences between fluid densities which result due to temperature changes. Forced convection uses externally induced flow, such as wind. The heat transfer rate for convection is given by the following equation: where h is the convection coefficient, A is the surface area, and T surface and T ∞ are the surface and ambient temperatures, respectively. Th convection coefficient is a measure of how effective a fluid is at carrying heat to and away from the surface. It is dependent on factors su the fluid density, velocity, and viscosity. Generally, fluids with higher velocity and/or higher density have greater h . 5.2 Natural Convection The convection coefficient for natural convection in gas is generally between 1 W/m 2
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